First off, I would recommending doing some research into what your school/district does for gifted students as well as what are the state laws. Do they have gifted programs? If so, when do they start? What are the requirements to enter them? Are there non-public options that you would consider? (essentially what are your options and what (if anything) might you need to open those doors)
For schools that have programs, sometimes they have testing timelines and requirements that would be good to know before paying to test privately (certain tests, within a year or after age x for example). You might also be able to get the school to do the testing which will save money.
The answers to those would impact IF I was going to test (or possible impact the timing). Other things I would consider on the IF side are - do you think there might be more than gifted going on (LD's, ASD, ADHD, anxiety, etc)? Is school not going well and you need something to back you up in order to make school less painful?
"HOW to utilize your resources to get in a school environment where he can thrive" is a bigger question/challenge and depends on some of the questions above. Once you have an idea of what the options are then it is a matter of gathering info to figure out what the best fit might be and/or how to make advocate to improve a less than ideal fit.
My answer would also depend on how challenging it is for you to pay for testing and how cooperative you think he might be. If financially it isn't a huge hardship and you're willing to risk having to retest again my answer would be different than a situation where it would cause financial stress and you have one shot for example. It can be challenging to get accurate results with younger children (I say this based on my experience of testing a 6.5 year old that was NOT cooperative - I don't regret testing because we HAD to at the time and it helped but we did have to retest later which gave us more accurate results (or at least ones that seem to more closely match the kid we know)).
